Capstan friction drive apparatus of tape recorder

ABSTRACT

The invention relates to a friction drive apparatus of a tape recorder which has a capstan and a friction wheel which is brought into slidable contact with a flywheel on which the capstan is mounted, the friction wheel serving to transmit a rotational force to the flywheel, the apparatus being constructed such that there are provided a support mechanism for pivotally supporting the friction wheel about a pivotal point which is eccentric with respect to a rotating shaft of the friction wheel, and biasing means for pivotally biasing the friction wheel about the pivotal point in a contact surface direction of the flywheel, the biasing means being arrranged to apply a predetermined initial contact pressure between the friction wheel and the flywheel, and a rotational direction of the friction wheel being determined such that a reaction force at the contact surface upon rotation of the friction wheel acts in a direction to cause pivotal movement of the friction wheel in the same direction as a direction toward which the biasing means acts, thereby increasing a contact pressure between the friction wheel and the flywheel above the initial contact pressure. 
     The support mechanism pivotally supports a motor through a pair of support members which are respectively disposed in front of and behind the motor, so that the friction wheel mounted on the rotating shaft of the motor is supported, the pair of support members being disposed in symmetrically eccentric positions with respect to the rotating shaft of the motor, and a line connecting the support members being drawn to pass through a center of gravity of the motor.

TECHNICAL FIELD

The present invention relates to a capstan friction drive apparatus of atape recorder which has a capstan and a friction wheel which is broughtinto slidable contact with a flywheel on which the capstan is mounted,the friction wheel serving to transmit a rotational force to theflywheel.

BACKGROUND ART

In general, in a friction drive apparatus such as a disk drive system, amaterial such as rubber which has a considerably large frictioncoefficient is used to cover at least one of two opposing contactsurfaces, so that a sufficient contact pressure acts between these twosurfaces, thereby transmitting the rotational force through a sufficientfriction force. However, when a friction drive apparatus is not used fora long period of time, a rubber surface which has been in tight contactwith the opposing contact surface becomes locally recessed, since therubber surface deforms over time. When the friction drive apparatus isrotated again under this condition, the local recess results inmechanical vibration. In particular, in electronic equipnent such as acassette tape recorder which is greatly affected by mechanicalvibration, the deformation over time described above has the effect ofdegrading wow and flutter characteristic. In addition, the deformationcauses noise and vibration.

On the other hand, when a friction wheel which is biased to apply apredetermined contact pressure is directly coupled to a motor shaft, thebiasing force is affected by the self-weight of the motor. The contactpressure between the friction wheel and the flywheel varies inaccordance with an orientation of the tape recorder. In this manner, theself-weight of the motor affects and degrades precision and reliability.

OBJECT OF INVENTION

The present invention has been made to overcome the conventionalproblems described above, and has as its object the provision of acapstan friction drive apparatus of a tape recorder, wherein a frictionsurface is not subjected to deformation over time (e.g., recess) even ifthe apparatus will not be used for a long period of time, by decreasingan initial contact pressure and at the same time a sufficient frictionalforce is provided during rotation, thereby transmitting thepredetermined rotational force.

It is another object of the present invention to provide a capstanfriction drive apparatus of a tape recorder, wherein a contact pressurebetween the friction wheel and the flywheel will not vary by aself-weight of a motor when the friction wheel is directly coupled tothe motor shaft.

SUMMARY OF INVENTION

In order to achieve the above objects of the present invention, there isprovided a friction drive apparatus of a tape recorder which has acapstan and a friction wheel which is brought into slidable contact witha flywheel on which the capstan is mounted, the friction wheel servingto transmit a rotational force to the flywheel, wherein there areprovided a support mechanism for pivotally supporting said frictionwheel about a pivotal point which is eccentric with respect to arotating shaft of said friction wheel, and biasing means for pivotallybiasing said friction wheel about said pivotal point in a contactsurface direction of said flywheel, said biasing means being arranged toapply a predetermined initial contact pressure between said frictionwheel and said flywheel, and a rotational direction of said frictionwheel being determined such that a reaction force at said contactsurface upon rotation of said friction wheel acts in a direction tocause pivotal movement of said friction wheel in the same direction as adirection toward which said biasing means acts, thereby increasing acontact pressure between said friction wheel and said flywheel above theinitial contact pressure.

Said support mechanism pivotally supports a motor through a pair ofsupport members which are respectively disposed in front of and behindsaid motor, so that said friction wheel mounted on said rotating shaftof said motor is supported, said pair of support members being disposedin symmetrically eccentric positions with respect to said rotating shaftof said motor, and a line connecting said support members being drawn topass through the center of gravity of the motor.

In the capstan friction drive apparatus of a tape recorder which has theabove-mentioned construction according to the present invention, thefriction surface will not deform over time even if it is not used for along period of time. At the same time, a sufficient frictional forceacts between the friction wheel and the flywheel during rotation.Therefore, a predetermined rotational force can be properly transmitted.

On the other hand, when the friction wheel is directly coupled to themotor shaft, a contact pressure between the friction wheel and theflywheel which is conventionally influenced by the self-weight of themotor will not vary, irrespective of the orientation of the taperecorder.

The drawings show an embodiment of a tape drive mechanism of a cassettetape recorder to which the present invention is applied, in which

FIG. 1 is a schematic plan view showing a stop mode of the tape driveapparatus on a mechanism chassis,

FIG. 2 is a perspective view showing a support state of a motor,

FIG. 3 is a developed perspective view thereof,

FIG. 4 is a perspective view showing a state removed the fixing memberof the motor suppport member from FIG. 2,

FIG. 5A is a longitudinal sectional view of a vibration-preventiverubber member of the motor,

FIG. 5B is a sectional view thereof taken along the line B--B of FIG.5A,

FIG. 5C is a sectional view thereof taken along the line C--C of FIG.5A,

FIG. 6 is a sectional view taken along the line VI--VI of FIG. 2,

FIG. 7 is a sectional view taken along the line VII--VII of FIG. 2,

FIG. 8 is a longitudinal sectional view of a capstan pulley,

FIGS. 9A and 9B are views showing the principle of the motor supportstructure, in which FIG. 9A is a side view thereof and FIG. 9B is afront view thereof,

FIG. 10 is a front view showing a drive section when viewed from themotor pulley side so as to explain the principle of the friction drivesection, and

FIG. 11 is a schematic plan view showing the motor support structure soas to explain the fine adjustment mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment will be described with reference to the accompanyingdrawings in which the present invention is applied to a tape driveapparatus of a cassette tape recorder.

The tape drive apparatus will be schematically described with referenceto FIG. 1. This tape drive apparatus is mounted on a backside surface ofa mechanism chassis 1 which opposes a cassette mounting surface thereof.Therefore, in FIG. 1, a supply reel shaft 2, a take-up reel shaft 3 anda capstan 4 extend downward from the mechanism chassis 1. These driveshafts are supported by the mechanism chassis 1 and also extend upwardtherefrom.

A motor 5 is supported by a motor support member 6 disposed on thechassis 1. A motor pulley 8 fixed on a motor shaft 7 of the motor 5presses against the lower portion of a capstan pulley 9, which alsoserves as a flywheel, fixed on the upper end of the capstan 4. The motorpulley 8 serves to drive the capstan 4 with a frictional force. A drivegear shaft 10 is vertically mounted on the upper surface of the chassis1 at an intermediate position among the supply reel shaft 2, the take-upreel shaft 3 and the capstan 4. In addition, a conversion gear shaft 11is vertically mounted on the upper surface of the mechanism chassis 1 atan intermediate portion between the drive gear shaft 10 and the supplyreel shaft 2.

A capstan gear 12 comprising a wide face-width gear is mounted on thelower portion of the capstan pulley 9. First and second drive gears 13and 14 are rotatably mounted on the drive gear shaft 10 such that aclutch mechanism (not shown) is interposed between the first and seconddrive gears 13 and 14 which are movable along the axial directionthereof. It should be noted that the second drive gear 14 is coupled tothe first drive gear 13 through the clutch mechanism, so that the seconddrive gear 14 is coaxially rotated together with the first drive gear13. During rotation of the second drive gear 14, the second drive gear14 can be rotated or stopped in accordance with a load acting thereon.

A conversion gear 15 comprising a wide face-width gear is rotatablymounted on the conversion gear shaft 11 such that the conversion gear 15can be moved along the axial direction thereof. This wide face-widthgear 15 is biased by a compression spring (not shown) upward in FIG. 1.A supply reel shaft gear 16 comprising a wide face-width gear is mountedon the supply reel shaft 2 at an upper surface side of the mechanismchassis 1. First and second take-up reel shaft gears 17 and 18 aremounted on the take-up reel shaft 3 at an upper surface side of themechanism chasses 1. surface side of t

The first drive gear 13 is always meshed with the capstan gear 12 andcan be axially moved to be selectively meshed with the conversion gear15 and the first take-up reel shaft gear 17. Similarly, the conversiongear 15 is always meshed with the supply reel shaft gear 16 and can beaxially moved. The second drive gear 14 is engaged with or disengagedfrom the second supply reel shaft gear 18 upon axial movement of thesecond drive gear 14.

On the other hand, an operation plate shaft 19 is vertically fixed onthe upper surface of the mechanism chassis 1. A first operation plate 21is mounted on the operation plate shaft 19 through a sleeve 20 which isaxially slidable. A distal end 21a of the first operation plate 21 isengaged with an annular groove formed in a boss of the first drive gear13. The first operation plate 21 can be vertically moved together withthe first drive gear 13. A second operation plate 22 is disposed betweenthe sleeve 20 of the operation plate shaft 19 and the first operationplate 21. The second operation plate 22 comprises a leaf spring. Adistal end 22a of the second operation plate 22 is fitted outside theconversion gear shaft 11 and is brought into tight contact with theupper surface of the conversion gear 15.

A play button (reproduction button) 23 is constructed such that theconversion gear 15 is moved downward when the distal end 22a of thesecond operation plate 22 is moved downward. A fast forward button 24serves to move the first and second operation plates 21 and 22 to theirlowermost position, so that the first drive gear 13 is meshed with thefirst take-up reel shaft gear 17. A rewind button 25 serves to move thefirst operation plate 21 to an intermediate position such that the firstdrive gear 13 is meshed with the conversion gear 15. A stop button 26serves to release the locked states of the operation buttons 23, 24 and25 at the active positions thereof to return these buttons to theirinactive positions.

Referring to FIG. 1, reference numeral 27 denotes a play head mounted onthe back side of the mechanism chassis 1. A magnetic tape (not shown)travels past a front portion 27a of the play head 27, passes between apinch roller 28 and the capstan 4, and is taken up by the take-up reelmounted on the take-up reel shaft 3.

The tape drive operation of the tape drive apparatus having theconstruction shown in FIG. 1 will be schematically described withreference to FIG. 1.

In the stop mode, the first and second drive gears 13 and 14 are locatedat their respective uppermost positions. The second drive gear 14 ismeshed with the second take-up reel shaft gear 18, and the first drivegear 13 is located above the conversion gear 15 with a predetermined gaptherebetween.

When a user presses the play button 23 in the stop mode, the conversiongear 15 is moved downward, so that the gap between the first drive gear13 and the conversion gear 15 is increased. At the same time, the motor5 is rotated in the direction indicated by arrow a in FIG. 1, so thatthe capstan 4 is rotated in the direction of arrow b. The take-up reelshaft 3 can be driven in the direction of arrow d through the capstangear 12, the first drive gear 13, the clutch mechanism, the second drivegear 14 and the second take-up reel shaft gear 18, thereby setting thetape recorder in the play mode (FWD or forward tape travel state).

When the user depresses the fast forward button 24 in the stop mode, thefirst and second operation plates 21 and 22 are moved downward to theirrespective lowermost positions. Along with this downward movement, thefirst and second drive gears 13 and 14 are moved downward to theirlowermost positions. The second drive gear 14 is disengaged from thesecond take-up reel shaft gear 18, and the first drive gear 13 is meshedwith the first take-up reel shaft gear 17. It should be noted that thefirst drive gear 13 is moved together with the conversion gear 15 withthe predetermined gap therebetween, and will not be meshed with theconversion gear 15. Therefore, the fast forward button 24 is locked atthe active position, so that the take-up reel shaft 3 is rotated in thedirection indicated by arrow d through the capstan gear 12, the firstdrive gear 13 and the first take-up reel shaft gear 17, thereby settingthe tape recorder in the fast forward mode (FF or fast forward tapetravel state).

When the user presses the rewind button 25 in the stop mode, the firstoperation plate 21 is moved halfway downward, and the first and seconddrive gears 13 and 14 are also moved to an intermediate position. Thesecond drive gear 14 is disengaged from the second take-up reel shaftgear 18, but the first drive gear 13 does not become meshed with thefirst take-up reel shaft gear 17. Instead, the first drive gear 13meshes with the conversion gear 15. Therefore, the rewind button 25 islocated in the active position, so that the supply reel shaft 2 isrotated in the direction indicated by arrow f through the capstan gear12, the first drive gear 13, the conversion gear 15 and the supply reelshaft gear 16, thereby setting the tape recorder in the rewind mode(tape REW or rewind travel state).

The motor support structure will now be described in detail withreference to FIGS. 2 to 7.

As shown in FIG. 3, cylindrical vibration-preventive rubber members 30(FIGS. 5A-5C) are mounted on both ends of the motor 5, respectively, andare formed integrally with the motor 5. A shield plate 31 covers theouter surface of the motor 5. A rear side plate 32 of the motor 5 isintegrally mounted on a boss portion of the corresponding rubber member30 at a rear portion of the motor 5. Similarly, a front side plate 34 ofa motor mounting member 33 is integrally mounted on a boss portion ofthe corresponding rubber member 30 at a front portion of the motor 5.The boss portion of each rubber member 30 comprises a toothed portion30a formed radially along the peripheral surface of the boss, and aring-like portion 30b. Through holes 32a and 34a formed at the centralportions of the side plates 32 and 34, respectively, have a diameterslightly smaller than the outer diameter of the ring-like portion 30b.When the side plates 32 and 34 are respectively fitted around thetoothed portions 30a, the portions 30a are deformed so that the sideplates 32 and 34 are firmly fixed around the portions 30a. In addition,the ring-like portions 30b serve as collar portions, so that the sideplates 32 and 34 will not be removed from the ring-like portions 30b, asif the side plates 32 and 34 were fitted in annular grooves,respectively. A fixing pin 35 is integrally formed at a predeterminedposition of the side plate 32 to be perpendicular with respect to thesurface of the side plate 32. On the other hand, a rear connecting plate36 which is parallel to the front side plate 34 is formed on the motormounting member 33. The rear connecting plate 36 is integrally connectedto the front side plate 34 by connecting members 37 to constitute aU-shaped structure. When the rear side plate 32 and the front side plate34 are mounted on the rubber members 30, respectively, as describedabove, the rear connecting plate 36 is disposed outside the rear sideplate 32. An engaging portion 36a having a semicircular engaging groove36c engages with the fixing pin 35. By screwing a screw 38 through athrough hole 36b of the connecting plate 36 and into a female threadhole 32b of the rear side plate 32, the rear side plate 32 is connectedto the motor mounting member 33. As a result, as shown in FIG. 4, themotor 5 is integrally formed with these rigid members. The fixing pin 35is substantially parallel to the motor shaft 7. An arm 39 extends to theleft from the front side plate 34 to be substantially horizontal. Aspring seat 40 is formed at the distal end of the arm 39. A through hole41 is formed at an edge of the rear side plate 34.

As shown in FIG. 3, the motor support member 6 comprises a fixing member43 which is fixed on the mechanism chassis 1, and an adjustment plate44. The fixing member 43 has an integral construction constituted by aright horizontal member 45 bent perpendicularly downward, a right legportion 46 for supporting the horizontal member 45 on the mechanismchassis 1, a substantially horizontal extending member 47 which extendsto be perpendicular from the rear end of the horizontal member 45 towardthe motor side, a short left horizontal member 48, a left leg portion 49and a connecting member 50 for connecting the right and left horizontalmembers 45 and 48. The fixing member 43 supports the motor 5 togetherwith the motor mounting member 33. The fixing member 43 is fixed at apredetermined position on the mechanism chassis 1 by screws extendingthrough screw holes 51 of the leg portions 46 and 49. A through hole 52is formed in the extending member 47 at a position corresponding to thefixing pin 35 of the rear side plate 32, so as to receive the pin 35. AnL-shaped notch 53 is formed in the side surface of the front portion ofthe horizontal member 45. Two elongate holes 54 and 55 are verticallyformed in the left leg portion 49. A screw hole 57 is formed in the leftleg portion 49 at a middle portion between the two elongate holes 54 and55, so as to receive an adjusting screw 56. A large opening 58 whichreceives the arm 39 or the like of the front side plate 34 is formed inthe vicinity of the elongate holes 54 and 55 and the screw hole 57.

A through hole 60 is formed at the center of the adjustment plate 44.The motor shaft 7 and the motor pulley 8 extend through the through hole60. A fixing pin 61 is integrally formed with the ajustment plate 44 tobe substantially perpendicular to the surface of the side plate 34 at aposition corresponding to the through hole 41 of the front side plate34. The fixing pin 61 can be fitted in the through hole 41. A guideportion 62 which has a rectangular cross-sectional shape and extendshorizontally is formed at the right portion of the adjustment plate 44.The guide portion 62 can be fitted in a longitudinally elongate hole 53aof the L-shaped notch 53 of the horizontal member 45, to be slidable inthe elongate hole 53a. A projection 63 that functions as a spring seatis formed at a predetermined position of the upper portion of the guideportion 62. Two further guide portions 64 and 65 each of which has arectangular sectional shape extend horizontally from the left portion ofthe adjustment plate 44 at positions corresponding to the elongate holes54 and 55 of the leg portion 49, and can be slidably fitted in theelongate holes 54 and 55.

In order to mount the motor 5 on the motor support member 6, acompression coil spring 66 is fitted to the guide portion 62 of theadjustment plate 44, and then the guide portions 62, 64 and 65 arefitted in the corresponding elongate holes 53a, 54 and 55. The motor 5together with the motor mounting member 33 is inserted in a spacedefined by the adjustment plate 44 and the extending member 47 of thefixing member 43 of the motor support member 6. By utilizing the elasticforce of the extending member 47, the fixing pins 35 and 61 arerespectively fitted in the corresponding through holes 52 and 41. Theadjusting screw 56 is screwed into the screw hole to adjust the motorpulley 8 to a predetermined position. On the other hand, a predeterminedtension coil spring 67 is hooked between the spring seat 40 of the arm39 of the front side plate 34 and the through holes 51 of the legportion 49. Thus, assembly can be performed to obtain a unit as shown inFIG. 2. In this case, the fixing pin 61 is substantially parallel to themotor shaft 7. The motor 5 is integrally assembled together with themotor mounting member 33, so that the motor 5 is pivotally mounted onthe motor support member 6 through the fixing pins 35 and 61. Inaddition, the motor 5 is biased by the tension coil spring 67 to bepivoted about the fixing pins 35 and 61.

The fixing pins 35 and 61 oppose each other and are inclined at an angleof about 45 to the right and left with respect to a motor axis 0, asshown in FIG. 9B. The fixing pins 35 and 61 are disposed such that eachis spaced a distance l away from the axis 0.

The capstan pulley 9 will now be described with reference to FIG. 8.

The capstan 4 is supported by a bearing 69 fixed on the mechanismchassis 1, and is rotatable. The capstan pulley 9 having a disk shapewith an annular groove at an intermediate portion thereof, is fixed atthe upper end of the capstan 4 as described before. The capstan gear 12having a wide face-width is fixed at the lower portion of the capstan 4.The capstan gear 12 is supported by the outer surface of the bearing 69and is rotated together with the capstan pulley 9. An annular rubbermember 70 is fixed on the lower surface side of the peripheral surfaceof the capstan pulley 9 and has a contact surface of a moderatelyconical shape. The contact surface of the motor pulley 8 which isbrought into tight contact with the conical contact surface of theannular rubber member 70 also comprises a conical shape of the sameangle. An annular magnetic rotor member 72 is fixed in the annularrecess of the capstan pulley 9, and has a plurality of radial teeth 71formed in its inner surface 9 at equal intervals.

A magnetic stator member 74 is disposed in an inner part of the annularrecess and has a plurality of teeth 73 formed in its outer surface andwhich are spaced a predetermined distance apart from the teeth 71 of therotor member 72 so as to oppose the teeth 71 of the rotor member 72. Theteeth 73 have the same pitch as that of the teeth 71. An annular magnet75 is disposed in the stator memeber 74 such that, for example, theupper surface of the magnet 75 constitutes the N pole and the lowersurface thereof constitutes the S pole, so as to form a magnetic pathbetween the rotor member 72 and the stator member 74. Therefore, achange in magnetic flux between the irregular pattern formed by theteeth 71 of the rotor side during rotation and the irregular patternformed by the teeth 73 is extracted as an output signal. Therefore,velocity detection based upon the output of a frequency generator can beperformed. It should be noted that the stator member 74 is integrallycoupled to a support plate 77 (whose shape is illustrated in FIG. 1)through a center member 76, and is fixed by a screw 79 to a column 78extending vertically upward from the mechanism chassis 1.

Reference numeral 80 denotes a pivot bearing which is made of teflon orthe like, which has a male thread on its outer surface, and which has aconical recess 80a at the center thereof. The pivot bearing 80 issupported at the recess 80a on a conical top portion 4a of the capstan 4to hold the stator side at a proper position with respect to the axis ofthe capstan 4. Therefore, a space between the teeth 71 of the rotormember 72 and the teeth 73 of the stator member 74 is uniform over theentire peripheral portions thereof. In order to mount the stator member,an inner surface 82 of the circular recess of the stator member islocated on an outer surface 81 of a circular boss which is located atthe center of the capstan pulley 9. Thereafter, the support plate 77 isset by the screw 79. When the pivot bearing 80 is then screwed in, theconical recess 80a of the pivot bearing 80 is screwed down along conicaltop portion 4a of the capstan 4, so that the axis of the pivot bearing80 can coincide with the axis of the capstan 4. Therefore, the statormember 74 mounted integrally with the pivot bearing 80 can befine-adjusted together with the center member 76 and the support plate77, to be aligned with the axis of the capstan 4.

The operation and effect of the motor and the motor pulley which aresupported as described above will now be described.

Referring to FIGS. 9A and 9B, the front portion of the motor 5(including the motor mounting member 33 mounted together with the motor5) is pivotally supported by the fixing pin 61, and the rear portion ofthe motor 5 is pivotally supported by the fixing pin 35. When loadscaused by the self-weight W of the motor 5 which are applied to thefixing pins 61 and 35 are defined as W₁ and W₂, the front portion of themotor 5 is pivoted clockwise by a moment W₁ m₁, and the rear portion ofthe motor 5 is pivoted counterclockwise by a moment W₂ m₂. The fixingscrews 35 and 61 lie opposite each other on a line inclined with respectto the axis 0 of the motor, and are equidistantly spaced by the distancel from the axis 0, so that the relation m₁ =m₂ is established. A lineconnecting support points R and S of the pins 35 and 61 supported by themotor support member 6 passes through substantially the center ofgravity of the motor 5 in FIG. 9A, so that the relation W₁ =W₂ =W/2 isestablished. Since W₁ m₁ =W₂ m₂, the motor 5 will not rotate due to itsself-weight. However, since the mctor 5 is pivotally supported by thefixing pins 35 and 61, the motor 5 can be pivoted about the pins 35 and61.

The friction driving by the motor pulley 8 will now be described. Asshown in FIG. 6, the arm 39 of the front side plate 34 is biaseddownward by the tension coil spring 67. Therefore, the motor 5 and hencethe motor pulley 8 is pivoted about the pivot point 61 in the directionindicated by arrow g, as shown in FIG. 10. The motor pulley 8 is urgedagainst the rubber member 70 of the capstan pulley 9. Under this initialcontact pressure, when the motor pulleY 8 is rotated in the direction ofarrow a, as shown in FIG. 1, the motor pulley 8 causes the capstanpulley 9 to rotate in the direction of arrow b by the rotational force Pcorresponding to the initial contact force. A reaction force P'corresponding to the rotational force P acts on the contact surface ofthe motor pulley 8 in the direction of arrow i opposite to the directionof arrow b. The reaction force P' acts to move the motor shaft 7 in thedirection of arrow i, so that the motor pulley 8 is pivoted about thepivot point 61 by a moment comprising a product P".l of the tangentialcomponent of P" and the radius l in the direction of arrow g, as shownin FIG. 10. By this pivotal force, the motor pulley 8 is urged againstthe capstan pulley 9 at a contact pressure greater than the initialcontact pressure. As a result, the rotational force P is furtherincreased. When the frictional force increases in the process describedabove so as to become equal to a load of the capstan pulley 9, thecapstan pulley 9 is started, and normal operation is performed.

The initial contact pressure can be as low as a minimum force requiredto prevent slippage of the motor pulley 8 with respect to the capstanpulley 9. During operation, the motor pulley 8 is automatically urgedagainst the contact surface of the capstan pulley 9, so that the contactpressure is gradually increased, and thus the capstan pulley 9 is drivenin accordance with the contact pressure corresponding to the load. Forexample, the conventional cassette tape recorder of similar typerequires a contact pressure of 90 to 100 g. However, the cassette taperecorder of the present invention only requires an initial contactpressure of 20 to 30 g. An angle α in FIG. 10 preferably falls withinthe range of 120° to 150°.

Furthermore, in this embodiment, since the motor is supported so as notto pivot due to its self-weight, the initial contact pressure is notinfluenced by the self-weight of the motor. For this reason, a highlyprecise initial contact pressure can be given and can be minimized.

The fine-adjustment function of the fine-adjustment mechanism will nowbe described. As shown in FIG. 7, the adjustment plate 44 of the motorsupport member 6 is supported such that the arms 62, 64 and 65 arerespectively slidably fitted in the elongate holes 53a, 64 and 65 of thefixing member 43, as previously described. The adjusting screw 56 isused to adjust the motor support member 6 to be substantially horizontalin the right-left direction (y-direction). On the other hand, the motor5 is pivotally supported together with the motor mounting member 33 bythe adjustment plate 44 by means of the pin 61 fixed on the adjustmentplate 44. Therefore, when the adjustment plate 44 is slightly moved fromthe position indicated by the solid line to the right-hand positionindicated by the alternate long and short dashed line in FIG. 7 (andFIG. 11,) the fixing pin 61 is horizontally moved to the right by anamount for fine adjustment. As previously mentioned, the motor 5 issupported by the fixing pins 35 and 61, and the rear side fixing pin 35will not move. When the support point S of the front side fixing pin 61is moved, the motor 5 is pivoted about the support point R of the rearside fixing pin 35. Therefore, the axis of the motor is also pivoted bythis amount. For example, the axis is deviated by x from the center Q ofthe capstan pulley 9. In other words, the motor pulley 8 is set at adeviated position. The motor pulley 8 is moved along the right-leftdirection by means of the adjusting screw 56 while the magnetic tapetravels and the reading of the measuring equipment is observed, therebythe motor pulley 8 can be set at a position where a wow and fluttervalue becomes minimum.

In the capstan friction drive apparatus of a tape recorder according tothe present invention as described above, even if the initial contactpressure between the friction wheel and the flywheel is minimized, thefriction wheel is urged against the contact surface upon starting of theapparatus. The contact pressure is increased, so that the rotationalforce corresponding to the load of the flywheel can be transmitted. Inthe stop mode, the initial contact pressure as a minimum contactpressure is restored. Even if the apparatus is not used for a longperiod of time, the friction surface made of rubber will not deform overtime due to the contact pressure, thereby preventing local recessing ofthe friction surface. Therefore, the capstan friction drive apparatus ofthe present invention reduces irregular rotation, noise and vibrator andcan be suitable for delicate tape recorder driving.

According to the motor support mechanism of the present invention, themotor is pivotally supported through the pair of support members (pivotpins) respectively located in front of and behind the motor so as toprovide the contact pressure between the friction wheel and theflywheel. However, the motor will not pivot about the pair of supportmembers even if its self-weight acts thereon. The self-weight of themotor will not influence the contact pressure. The contact pressure canbe held to be a predetermined pressure irrespective of an orientation ofthe tape recorder. As a result, a high-performance, high-reliabilitytape recorder can be obtained.

I claim:
 1. A friction drive apparatus for a tape recorder comprisingaflywheel, a capstan mounted on said flywheel, a motor, a friction wheelmounted on a rotary shaft of said motor and being adapted to be brouohtinto slidable contact with said flywheel on which said capstan ismounted for transmitting a rotational force to the flywheel, a supportmechanism for pivotally supporting said friction wheel about a pivotpoint which is eccentric with respect to said rotary shaft on which thefriction wheel is mounted, and biasing means for pivotally biasing saidfriction wheel about said pivot point toward a contact surface of theflywheel, said biasing means being adapted to apply a predeterminedinitial contact pressure between said friction wheel and flywheel, andthe direction of rotation of the friction wheel being determined suchthat a reaction force at said contact surface occurring upon rotation ofthe friction wheel acts in a direction which causes pivotal movement ofthe friction wheel in the same sense in which the biasing means acts,thereby increasing the contact pressure between the friction wheel andthe flywheel above said initial contact pressure, said support mechanismfor pivotally supporting said motor including a pair of support memberswhich are respectively disposed at opposite axial ends of said motor, soas thereby to support the friction wheel, the pair of support membersbeing disposed at symmetrically eccentric positions with respect to theaxial rotary shaft of the motor, and said pair of support members beingarranged such that a line passing therethrough also passes substantiallythrough the axial centre of gravity of the motor, whereby contactpressure between said friction wheel and said flywheel is independent ofthe weight of the motor.
 2. A friction drive apparatus according toclaim 1, in which said friction wheel has a leveled surface contactingsaid flywheel.
 3. A friction drive apparatus according to claim 1, inwhich said support mechanism comprises a metal bracket assembly havingat least two separable elements and said support members comprise firstand second pins arranged in respective holes in said bracket assemblyfor affixing said separable elements, one to another.
 4. A frictiondrive apparatus according to claim 3, further comprising rubber mountingmeans for resiliently mounting said motor to one of said two separableelements.
 5. A friction drive apparatus according to claim 4, furthercomprising position adjusting means interposed between said twoseparable elements mutually affixed by said first and second pins foradjusting the axial alignment of said motor in one of said two separableelements.
 6. A friction drive apparatus according to claim 5, in whichsaid position adjusting means includes a threaded element threadedlyengaged on one of two separable elements and contacting the other ofsaid separable elements and second biasing means for maintaining saidother elements in contact with said threaded element.